Integrated circuits (ICs) and other electronic devices often include arrangements of interconnected field-effect transistors (FETs), also called metal-oxide-semiconductor field-effect transistors (MOSFETs), or simply MOS transistors or devices. A typical MOS transistor includes a gate electrode and spaced-apart source and drain electrodes. A control voltage applied to the gate electrode controls the flow of current through a variably conductive channel between the source and drain electrodes.
Power transistor devices are designed to be tolerant of the high currents and voltages that are present in some applications. Some power transistor devices are also designed to handle radio frequency (RF) signals, such as the devices used in wireless communications and other RF power amplifier applications. One type of RF power transistor device is a laterally diffused metal-oxide-semiconductor (LDMOS) transistor. In an LDMOS device, charge carriers drift through a drift space between a channel region and the drain electrode under the electric field arising from an operating voltage applied between the source and drain electrodes.
The output power density and linear efficiency of an RF LDMOS transistor is affected by the transistor's drain-source capacitance, (Cds), drain-gate capacitance (Cdg), on-state drain-to-source resistance (Rdson), and source-to-drain breakdown voltage (BVdss). Generally, there is a desire in the industry to develop RF LDMOS transistors with higher power densities and improved linear efficiencies. Accordingly, there is a desire in the industry to develop RF LDMOS transistors with lower Cds, Cdg, and Rdson, and higher BVdss.